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pharmacogenics Flashcards

1
Q

pharmacodynamics

A

what the drug does to the body

mechanism of effect (action)
sensitivity
responsiveness

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2
Q

pharmacokinetics

A

what the body does to the drug

absorption
distribution
metabolism
excretion

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3
Q

central compartment blood and body mass

A

75% of blood flow, 10% body mass

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4
Q

a tissue that accumulates a drug preferentially may

A

act as a reservoir to maintain the plasma concentration and thus prolong its duration of action

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5
Q

Rate of transfer between central and peripheral compartments decreases

A

with aging !

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6
Q

pKa =

A

the pH at which 50% of a drug will be in its ionized form.

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7
Q

Blood brain barrier works by

A

the limited permeability characteristics of the brain capillaries

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8
Q

the only limitation to permeation of the CNS by lipid soluble, non-ionized drugs is

A

cerebral blood flow

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9
Q

Blood brain barrier can be overcome by

A

administration of large doses

or be disrupted by acute head injury or arterial hypoxemia

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10
Q

effect site equilibration time

A

time it takes from administration of an IV drug to effect of drug

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11
Q

Ke0

A

rate constant of ELIMINATION from EFFECT SITE

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12
Q

Vd formula

A

dose of IV drug / plasma concentration before any has been eliminated

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13
Q

volume of distribution is influenced by

A
  1. lipid solubility
  2. protein binding
  3. molecular size
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14
Q

A drug that is not very lipid soluble and highly protein bound

A

Will not be able to cross membranes (not lipid soluble), will be bound to plasma protein (high protein binding) and therefore will remain mostly in the PLASMA.

So it will have a SMALLER Vd.

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15
Q

A lipid-soluble drug that is highly concentrated in tissues with a resulting low plasma concentration

A

will have a calculated Vd that exceeds total body water

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16
Q

Elimination Half Time

A

the time it takes for the PLASMA CONCENTRATION of a drug to decline 50% during elimination phase

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17
Q

Elimination half time is directly proportional to

A

volume of distribution

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18
Q

elimination half time is independent of

A

dose of drug administered

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19
Q

Elimination half time is inversely proportional to

A

clearance of drug

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20
Q

Near total (96.9%) elimination of drug from body requires

A

5 elimination half times

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21
Q

Elimination half life

A

time it takes to eliminate 50% of drug from BODY after its IV injection

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22
Q

Context Sensitive Half Time

A

time it takes for 50% decrease in plasma concentration of drug AFTER DISCONTINUATION OF IV INFUSION

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23
Q

Context sensitive half time depends on

A

Distribution AND excretion

physiochemical properties of the drug AND length of infusion

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24
Q

Context sensitive halftime relates to elimination half time

A

Context sensitive half time bears no constant relationship to the drugs elimination half-time

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25
Q

System absorption depends on

A

System absorption, regardless of route, depends on the drugs solubility

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26
Q

Disadvantages of oral administration

A

emesis, destruction by enzymes or acidic gastric fluid, irregular absorption with food or other drugs.

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27
Q

Principle site of drug absorption after PO administration is

A

small intestine r/t large surface area

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28
Q

changes in pH of GI fluid that favor the presence of a drug in its non-ionized form

A

favor systemic absorption

lipid-soluble

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29
Q

First Pass Hepatic Effect happens because

A

Drugs absorbed in the GI system first enter the portal venous blood and pass through the liver BEFORE entering the systemic circulation [[for delivery to tissue receptors]]

drugs in the liver are extensively metabolized.

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30
Q

reason for large differences between bioavailability of PO and IV drugs is

A

first pass hepatic effect

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31
Q

Sublingual/transmucosal administration is characterized by

A

rapid onset, bypasses the liver so no first pass hepatic effect.

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32
Q

Transdermal administration characteristics

A

provides sustained therapeutic plasma []

absorption occurs along sweat ducts and hair follicles that function as diffusion shunts

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33
Q

Things that affect the skin’s permeability to drugs

A

thickness and blood flow

why scopolamine goes behind the ear and not on your hand

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34
Q

Rectal administration, proximal vs distal

A

proximal rectal administration is absorbed by superior hemorrhoid veins to portal vein so FIRST PASS EFFECT.

Distal rectal administration bypasses the portal system

Difference is why drug administration via rectum is unpredictable.

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35
Q

Most drugs are present in both

A

ionized and non-ionized forms.

Because most drugs are WEAK ACIDS OR BASES.

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36
Q

ionized fraction of drugs are excreted

A

by the kidneys unchanged.

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37
Q

Degree of ionization depends on

A

the drugs dissociation constant pK and the surrounding pH

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38
Q

Changes in pH can affect

A

the degree to which a drug ionizes

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39
Q

When the pK = pH

A

50% of the drug is in its ionized form and 50% of the drug is non-ionized (lipid-soluble)

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40
Q

Ion trapping

A

ex. when a (basic) drug as lipid-soluble version crosses a membrane to a different environment (more acidic) and then ionizes.

Now ionized form is trapped on one side o membrane and also causes a concentration gradient for more of the drug to cross the membrane.

ex. placenta

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41
Q

Protein binding is inversely proportional to

A

Volume of distribution

42
Q

Unbound drugs in the plasma are more

A

easily metabolized and excreted

43
Q

Protein binding of drugs facilitates

A

elimination,

44
Q

Alterations in protein binding are more important for drugs that are

A

Highly protein bound (94 vs 96 compared to 70 vs 68)

45
Q

Low plasma concentration of drugs aren like to be more

A

highly protein bound than are higher plasma concentrations of the same drug

46
Q

Renal failure may decrease

A

the fraction of a drug bound to protein even in the absence of changes in plasma concentrations of albumin or other proteins.

–> something the kidneys usually excrete competes for binding sites on albumin

47
Q

clearance is defined as

A

volume of plasma cleared of drug by metabolism and excretion

volume of plasma cleared of drug per unit time

48
Q

almost all drugs administered in therapeutic dose range are cleared by

A

first order kinetics

at a rate proportional to the amount of drug present in the plasma

49
Q

Non organ clearance mechanisms

A

Hofmann Elimination and ester hydrolysis. Both happen in plasma

50
Q

Zero order kinetics

A

a constant amount of drug is cleared per unit of time.

when drugs exceed the metabolic or excretory capacity of the body to clear drugs by first order kinetics.

51
Q

Hepatic clearance is dependent on

A

blood and extraction ratio

52
Q

Hepatic extraction ratio >0.7

A

Perfusion-dependent elimination

increased blood flow = increased clearance
clearance will depend on hepatic blood flow.

53
Q

Hepatic extraction ratio <0.3

A

Capacity dependent elimination

A decrease in protein binding or an increase in enzyme activity will increase hepatic clearance.

54
Q

Most important organ for elimination of unchanged durgs

A

kidneys

55
Q

Highly lipid soluble drugs in the kidneys

A

Are reabsorbed

56
Q

Increased water solubility for a drug and Vd

A

Increased water solubility of drug DECREASES vd and would enhance its renal excretion

57
Q

zero order kinetics occurs when

A

the plasma concentration of a drug exceeds the capacity of metabolizing enzymes.

Reflects saturation of available enzymes and results in metabolism at a constant amount of drug per unit of time.

58
Q

Constant amount of drug metabolized per unit of time in zero order kinetics is dependent on

A

intrinsic activity of enzymes

59
Q

Four Basic Pathways of Metabolism

A

Oxidation, Reduction, Hydrolysis, Conjugation

60
Q

Phase I reactions of metabolism

A

Oxidation, reduction, hydrolysis

increase the drug’s POLARITY,

61
Q

Phase II reactions of metabolism

A

conjugation.

covalently link drug with highly polar molecule to make it water soluble enough for excretion

62
Q

Hepatic microsomal enzymes are involved in

A

oxidation, reduction, and conjugation

63
Q

CYP isozymes (6)

A 
CYP1A2
CYP2C9
CYP2C19
CYP2D6
CYP2E1
CYP3A1
64
Q

non-microsomal enzymes metabolize drugs mostly by

A

hydrolysis and conjugation

lesser degree oxidation, reduction

65
Q

receptor occupancy theory

A

the more receptors occupied by a drug the more effect

66
Q

non-receptor drug action

A

chelating drugs form bonds with metallic cations that may be found in body

67
Q

Agonist drugs

A

bind to sites and mimic cell signaling molecules , these cause similar effects at receptors

68
Q

Antagonist drugs

A

bind to receptors to prevent cell signally and block effect

69
Q

Enantiomers can exhibit differences in

A 
absorption 
distribution
clearance
potency 
toxicity (drug interactions)
70
Q

the therapeutically inactive isomer in a racemic mixture should be regarded as

A

an impurity

71
Q

efficacy

A

the ability of a drug to produce the desired therapeutic effect

72
Q

potency

A

the relationship between the therapeutic effect of a drug and the dose necessary to achieve that effect

73
Q

Increased affinity of a drug for its receptor

A

makes the drug more potent?

74
Q

Therapeutic index of a drug

A

ratio of LD50 to ED50

75
Q

commonly measured pharmacokinetic parameters of injected drugs are

A

elimination half time
bioavailability
clearance
volume of distribution

76
Q

LUNG uptakes

A

basic lipophilic drugs

77
Q

elimination half time and elimination half life are not equal when

A

the decrease in the drug’s plasma concentration does not parallel its elimination from the body

78
Q

context sensitive half time considers

A

the combined effects of distribution and metabolism as well as duration of continuous IV administration on drug pharmokinetics

79
Q

rate limiting step of transdermal administration =

A

diffusion across the stratum corneum of the epidermis

80
Q

Hoffman elimination / ester hydrolysis are responsible for the elimination of (4)

A

Succhs
atracurium
cisatricurium
mivacurium

81
Q

metabolism is defined as

A

biotransformation to convert pharmacologically active, lipid soluble drugs into water soluble and often inactive drugs

82
Q

increased water solubility of a drug reduces its

A

volume of distribution !

bc water soluble = ionized = in the plasma

83
Q

fraction of total drug eliminated during first order kinetics is

A

independent of the plasma concentration of drug.

  • attribute of the drug
84
Q

phase I reactions…

A

increase the drug’s polarity and prepare it for phase II

85
Q

phase II reactions…

A

covalently link the drug or metabolites with a highly polar molecule that renders it more water soluble for subsequent excretion

86
Q

hepatic microsomal enzymes are located

A

in the hepatic smooth ER

87
Q

CYP-450 involved in

A

OXIDATION, REDUCTION, and CONJUGATION of a large number drugs

88
Q

non-microsomal enzymes do not undergo

A

enzyme induction !!

which is why you can’t build a tolerance to succhs

89
Q

tachyphylaxis

A

tolerance that develops acutely with only a few doses of drug

90
Q

non receptor drug action:

A

ex. chelating drug

91
Q

immunity is present when

A

hypo-reactivity is due to the presence of antibodies

92
Q

clearance is directly proportional to

A

blood flow to clearing organ
extraction ratio
drug dose

93
Q

clearance is inversely proportional to

A

half-life

drug concentration in the central compartment

94
Q

albumin binds to

A

acidic drugs

95
Q

alpha1-acid-glycoprotein binds to

A

basic drugs

96
Q

beta globulin binds

A

basic drugs

97
Q

highly protein bound drugs typically have a slower rate of

A

metabolization and elimination

98
Q

drugs cleared by zero order kinetics even in therapeutic doses

A

aspirin, phenytoin, alcohol, warfarin, heparin, theophylline

99
Q

alt. pharmacodynamics

A

relationship between the effect site concentration and clinical effect

100
Q

alt. pharmokinetics

A

relationship between drug dose and plasma concentration

101
Q

context sensitive half time increases in parallel with

A

the length of infusion

pharm (4 decks)

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